C functions, that are equivalent to the Fortran subroutines, are available for those who prefer this language (indeed using IMG from C can seem more natural as IMG returns pointers to data). The major changes in the interface (compared with the Fortran specifications) are that the names of functions change from img_something or hdr_something to imgSomething and hdrSomething and that ``strings'' which are returned or can be passed as arrays also have a length argument.
IMG Simple Image Data Access